High voltage air terminal chamber for indoor power center with interlocks between fuse drawers and circuit breakers, fuse clamping and latching means, and universally pivotal terminal means

ABSTRACT

An indoor unit substation for supplying electrical power at distribution voltage includes an electrical transformer and an air terminal chamber enclosing terminating means for tap cables from a plurality of high-voltage primary feeder sources, a circuit interrupter for each source, and high-voltage fuses between the circuit interrupters and the transformer supported on horizontal drawout drawers in alignment with horizontal insulating bushings on the transformer. Manual fuse clamping means push the fuses into high-pressure contact with universal motion terminals on the transformer-insulating bushings, latching means are provided for the fuse drawers, and the fuse-clamping means prevent release of the drawer-latching means until clamping pressure is removed from the fuses. Interlock means prevents withdrawal of the fuse drawers if a circuit interrupter is closed, prevents closing of either circuit interrupter if a fuse drawer can be withdrawn, and prevents simultaneous closing of both circuit interrupters.

United-States Patent Thomas H. Keogh Pittsburgh;

Adolph E. Krupit, Allison Park, Pa. 768,81 1

Oct. 18, 1968 May 18, 1971 Allis-Chalmers Manufacturing Company Milwaukee, Wis.

inventors Appl. No. Filed Patented Assignee HIGH VOLTAGE AIR TERMINAL CHAMBER FOR INDOOR POWER CENTER WITH INTERLOCKS BETWEEN FUSE DRAWERS AND CIRCUIT BREAKERS, FUSE CLAMPING AND LATCHING MEANS, AND UNIVERSALLY PIVOTAL TERMINAL MEANS 55 Claims, 21 Drawing Figs.

[56] References Cited UNITED STATES PATENTS 1,402,123 1/1922 Wadsworth 2,086,424 7/ 1 937 Koehler 2,151,756 3/1939 Fletchereta1...........:::::

Goodman et al.

Primary Examiner-H. 0. Jones Assistant Examiner-Robert A. Vanderhye Attorneys-Lee H. Kaiser, Robert B. Benson and Thomas F.

Kirby ABSTRACT: An indoor unit substation for supplying electrical power at distribution voltage includes an electrical transfonner and an air terminal chamber enclosing terminating means for tap cables from a plurality of high-voltage primary feeder sources, a circuit interrupter for each source, and highvoltage fuses between the circuit interrupters and the transformer supported on horizontal drawout drawers in alignment with horizontal insulating bushings on the transformer. Manual fuse clamping means push the fuses into high-pressure contact with universal motion terminals on the transformer-insulating bushings, latching means are provided for the fuse drawers, and the fuse-clamping means prevent release of the drawer-latching means until clamping pressure is removed from the fuses. interlock means prevents withdrawal of the fuse drawers if a circuit interrupter is closed, prevents closing of either circuit interrupter if a fuse drawer can be withdrawn, and prevents simultaneous closing of both circuit interrupters.

10g #14 xxx- I!!! I 13/ :9 M L a) PATENTEUMAY18|97I 3579.045

sum 6 OF 6 HIGH VOLTAGE AIR TERMINAL CHAMBER FOR INDOOR POWER CENTER WITH INTERLOCKS BETWEEN FUSE DRAWERS AND CIRCUIT BREAKERS, FUSE CLAMPING AND LATCI-IING MEANS, AND UNIVERSALLY PIVOTAL TERMINAL MEANS This invention relates to indoor power centers, or unit substations which combine transformers and switchgear to supply electrical power at centers of load from high-voltage sources stepped down to service voltage, and in particular it relates to a unitary assembly of tenninating means for cables from a plurality of primary feeder sources, circuit breakers for the primary feeders, and primary protective equipment for such a load center. I

Indoor unit substations, termed power centers, using metalclad switchgear associated with air-insulated or noninflammable liquid-filled transformers are known for application in industrial plants having large floor space for installation of the substation. Electrical power is usually transmitted at high potential such as l5,000 volts to the power center where it is transformed to supply secondary distribution at 2,300 volts or to supply concentrated centers of load with power at service voltages such as 440 volts. Often the functions of transformation, regulation, protection, control and metering of electrical power are combined in a completely enclosed, factory assembled unit substation, but many industrial plants do not have sufficient floor space for such a unit substation, and known components to perform such functions as transformation and control are too heavy and bulky to permit mounting in an overhead location in an industrial plant for the purpose of conserving floor space in the plant.

It is an object of the invention to provide an indoor power center unitary assembly of terminating means for primary tap cables from a plurality of high-voltage primary feeder sources, a circuit breaker for each source, high-voltage protective means for the transformer, and interlocking means between the circuit breakers and between the breakers and the highvoltage protective means. It is a further object of the invention to provide such a unitary assembly which is substantially smaller and lighter than any arrangement of known components and which is sufficiently reduced in size and weight to permit overhead mounting in an indoor location in an industrial plant.

These and other objects and advantages of the invention will be more readily apparent from the following detailed description when considered inconjunction with the accompanying drawing wherein:

FIG. I is a schematic front view of an indoor unitary power center embodying the invention installed in any overhead location in an industrial plant;

FIG. 2 is a front view of the embodiment of the invention shown in FIG. I with a portion of the front wall broken away to illustrate the internal construction;

FIG. 3 is a plan view of the apparatus of FIG. 2 with a portion of the cover broken away;

FIG. 4 is a view taken along line lV-IV of FIG. 2;

FIG. 5 is a perspective view of the circuit breakers and bus bar connections between such breakers and the primary fuses of the apparatus of FIG. 2;

FIG. 6 is a view taken along line VI-VI of FIG. 3;

FIG. 7 is a view taken along line VII-VII of FIG. 3;

FIG. 8 is a view taken along line VIII-VIII of FIG. 7;

FIG. 9 is a view taken along line lX-IX of FIG. 7;

FIG. I0 is a view taken along line X-X of FIG. 2;

FIGS. 11 and 12 are perspective views respectively of the fixed and movable fiise trays of the apparatus of FIGS. 2-9;

FIG. 13 is a view taken along line XIII-XIII of FIG. 3 with the fuse removed;

FIG. 14 is a view taken along line XIV-XIV of FIG. 6 with the fuse removed;

FIGS. 15 and 16 are front and plan views respectively of the fuse tray cover; 1

FIG. 17 is a view taken along line XVII-XVII of FIG. 15 showing the closed and open positions of the fuse drawer latches in full and in dot-dash lines respectively;

FIG. 18 is an enlarged view taken along line XVIII-XVIII of FIG. 3;

FIG. 19 is a view taken along line XIX-XIX of FIG. 18;

FIG. 20 is a view taken along line XX-XX of FIG. 19; and

FIG. 21 is a view taken along line XXI-XXI of FIG. 6 with a wall of the air circuit breaker removed.

Referring to FIG. I of the drawing, an indoor power center for an industrial plant comprises a power transformer 10, a low-voltage circuit breaker 11 for the secondary distribution, and the primary voltage air terminal chamber 12 of the invention mounted on overhead, structural iron trusses 14 that are supported on vertical columns 15 which define a bay of an industrial plant. The indoor power center also includes tap junction boxes I6 which may be mounted on trays 17 for the threephase primary feeder cables I8 supported from the roof 19 of the industrial plant. Electrical power may be transmitted throughout the entire industrial plant at 15,000 volts over the three-phase primary feeder cables H8 in the trays I7, and junction, or taps are made in the T-junction boxes 16 between the primary feeder cables I8 and primary tap cables 20 and 21 (shown only as single lines in FIG. I) to transmit power at l5,000 volts to the air terminal chamber 12 mounted on the overhead trusses 14. The high-voltage electrical power is converted in transformer I0 from 15,000 volts to desired secondary potential such as 440 volts service voltage or 2,300 volts for secondarydistribution.

The T-junction box I6 is disclosed in the copending application of Thomas H. Keogh et al., Ser. No. 673,148, filed Oct. 5, I967, and having the same assignee as the present invention.

The primary voltage air terminal chamber 12 for the indoor power center comprises a unitary assembly of terminating means for the primary tap cables 20 and 21, primary circuit breakers 26 and 27 for the primary sources, current-limiting fuses 39 for the power center transformer 10, and interlocking means between primary circuit breakers 26 and 27 and the fuses 39 which prevent simultaneous closing of both primary circuit breakers, prevents primary circuit breaker closing when the fuses 39 are removed, and also preventsremoval of the fuses 39 when either primary breaker 26 or 27 is closed, and such air terminal assembly I2 occupies only a fraction of the space and weighs only a fraction of any arrangement of known components and is sufficiently small in size and light in weight to permit mounting on overhead trusses 14, thereby resulting in a substantial saving in floor space.

The air terminal chamber 12 is enclosed in a housing 22 (See FIGS. 2, 3, 4 and 6) of right-angle prism configuration sii'pported on a suitable base which may include a pair of elongated, horizontally spaced, structural iron channel members 23 (See FIGS. 2 and 3) disposed below the bottom wall of housing 22 and affixed at their ends by mounting brackets 24 secured to the web portion of a pair of the overhead trusses I4 of an industrial plant. Housing 22 of the primary voltage chamber I2 encloses a pair of three-phase, primary voltage load-break switches, or air circuit breakers 26 and 27 having elongated casings disposed back-to-back with their longitudinal axes in horizontal planes adjacent the bottom of housing 22 and each having three insulating bushings 28 projecting horizontally from the left end thereof and three insulating bushings 29 projecting horizontally from the right end thereof as shown in FIG. 2. The high-voltage, three-phase tape cables 20 and 21 from a pair of high-voltage sources such as the 15,000 volt primary feeder cables 18 in the cable trays 17 may terminate on the insulating bushings 28 of the primary circuit breakers 26 and 27 respectively.

The air circuit breakers 26 and 27 are opened and closed manually by operating handles 32A and 328 respectively (See FIGS. 2 and 6) accessible from the front of housing 22 to an operator on a catwalk (not shown) in the industrial plant. The power transformer 10 of the load center may include a casing 35 (See FIGS. 3 and 6) supported (by means not shown) on the trusses 14 and having three primary insulating bushings 36 extending horizontally therefrom through an aperture in the rear wall of housing 22 and into the interior of housing 22 and having terminal means 37 thereon which make electrical connection with metallic ferrules 38 on one end of three currentlimiting fuses 39 disposed horizontally above circuit breakers 26 and 27. Bus bars 42 (See FIGS. 2, 5, 6 and I3) electrically common the corresponding phase terminal means on insulating bushings 29 extending horizontally from the right end of both circuit breakers 26 and 27 (as seen in FIG. 2) and connect them to pivoted, vertically extending copper terminal bars 45 resiliently held against metallic ferrules 46 on the opposite end of current-limiting fuses 39. The current-limiting fuses 39 are supported within movable fuse trays 48 of suitable high dielectric strength insulating material and clamped under pressure between'the terminal bars 45 and the terminal means 37 on transformer-bushings 36 by elongated insulating rods 49 which normally are resiliently urged against the terminal bars 45.

The movable fuse trays 48 are affixed by pins 52 (See FIG. 14) to rectangular fuse tray covers 53 to form fuse drawers 54 which are reciprocable horizontally into and out of housing 22 through openings 55 (See FIGS. 13 and 14) in front wall 56 of housing 22 between the normal position shown in full lines, wherein the fuses 39 engage the terminal means 37 on the transformer bushings 36, and the open position shown in dotdash lines in FIG. 6 wherein the fuses 39 may be changed. Interlocking means described hereinafter prevent withdrawal of fuse drawers 54 until the operating handles 32A and 32B of both circuit breakers 26 and 27 are in open position. The insulating rods 49 are reciprocated within movable fuse trays 48 by externally threaded shafts 58 (See FIGS. 13 and 14) engaged within internally threaded openings 59 in rectangular covers 53 and having hand knobs 60 integral therewith external of housing 22. Resilient means for applying axial pressure against each fuse 39 operatively connects shaft 58 and insulating rod 49 and includes a first cup-shaped member 62 affixed to shaft 58 by a snapring, a smaller diameter second cupshaped member 63 affixed by a snapring to insulating rod 49 and telescoped within first cup-shaped member 62 so their open ends face each other, and a compression spring 64 disposed within the telescoped members 62 and 63.

The fuse drawers 54 are nonnally locked to housing 22 by U-shapeddrawer latches 66 (See FIGS. l5, l6 and 17) having horizontally extending ears 67 which protrude through eyes 68 on rectangular covers 53 and fit behind hook-shaped catches 70 on casing front wall 56. Fuse drawer latches 66 can be lifted to the dot-dash line position shown in FIG. 17 to remove the cars 67 thereon from behind the hook-shaped catches 70, but laterally projecting lugs 71 on latches 66 normally fit behind the rotatable fuse tightening knobs 60 and prevent lifting of latches 66. Ganged interfering arms 73 (See FIGS. 2, 3 and 14) are rotatable about parallel axes and normally disposed in a horizontal interfering position in front of the fuse-tightening knobs 60 to prevent rotation thereof in a direction to release pressure on current-limiting fuses 39. Until both circuit breaker operating handles 32A and 32B are in the open position, the ganged interfering anns 73 are prevented by interlocking means described hereinafter from being rotated to the vertical open position shown in dot-dash lines in FIG. 2. After the ganged arms 73 are rotated to the vertical open position, the rotatable fuse-tightening knobs 60 can be rotated in a direction to move the shafts 58 outward of casing 22 until the knobs 60 are in the dot-dash line position shown in FIGS. 14 and 17 wherein they no longer interfere with lugs 71 on drawer latches 66, thereby permitting the latches 66 to be pivoted upward until the hook portions 67 are out of the catches 70 to allow withdrawal of the fuse drawers 54 to the open position shown in dot-dash lines in FIG. 6. Movement of a shaft 58 outward of casing 22 by rotating hand knob 60 releases the pressure with which the compression spring 67 holds the fuse 39 against the tenninalmeans 37 of transformer bushing 36.

The three-phase primary tap cables 20 and 21 have three conductors 75 (See FIG. 3) which may be of 4/0 size each of which is surrounded by concentric layers of insulation 76 (See FIG. 3), semiconductive material 77, and a metallic grounding sheath 78. l'he insulation and semiconductive layers 76 and 77 are cut back and the edge of the semiconductive material 77 where the equipotential lines concentrate and the voltage gradient is the highest is covered with a mass 79 of moldable semiconductive material commercially available under the mark AIRSEAL to reduce the voltage gradient at this point. Flexible insulating boots 80 cover the joints between the cable conductors 75 and the bushing terminals and fit snugly at their ends over the bushings 28 and the insulation of the conductors. The cables 20 and 21 have outer layers of cable armor 81 which is cut back and extends into and is locked to a conventional cable terminator 82. The cable terminators 82 extend through vertically spaced cable entrance ports 83 in the left sidewall 84 of housing 22 (as seen in FIGS. 2 and 4) and are affixed to housing 22 with a hermetic sealby a resilient gasket and a nut 85 engaging external threads on cable terminator 82. The grounding sheaths 73 from the three conductors 75 of each tap cable 20 and 21 are electrically connected together internally of housing 22 and to a copper ground pad (not shown) on a wall of housing 22. Housing 22 preferably has a skeletal framework of elongated members such as angle iron members 86 (See FIG. 4), and removable panels 87 in the left end wall and removable panels 88 (See FIG. 3) in the front wall 56 are supported on studs 89 affixed to elongated members 86 to permit ready access to the cable terminations by the workman. I

An L-shaped barrier 90 which may be of sheet steel material extending between front and rear walls of housing 22 above upper circuit breakers 26 separates the air circuit breakers 26 and 27 from the current-limiting fuses 39. The bus bars 42A, 42B, and 42C have vertical portions (See FIGS. 5 and 6) which are connected to and electrically common the corresponding phase terminals on the insulating bushings 29 of both air breakers 26 and 27 and are bent over into horizontal portions 92 supported on standoff insulators 94 mounted on barrier 90. The horizontal portions 92A, 92B and 92C (See FIG. 5 of bus bars 42A, 42B and 42C are in the same horizontal plane. The horizontal portion 92A of bus bar 42A is a flat conductive plate electrically connected to vertical bus bar portion 42A, and the'portions 92B and 92C of bus bars 428 and 42C are integral therewith and L-shaped and of different lengths and terminate in alignment with portion 92A. Fixed insulating trays 96 of channel cross section for supporting the movable fuse trays 48 extend in a horizontal direction between the front and rear walls of housing 22 and are supported on standoff insulators 97 (See FIGS. 5, 6 and 13) mounted on the horizontal bus bar portions 928 and 92C and by L-shaped brackets 98 (See FIGS. 6 and 13) on the front wall 56 of housing 22. Pivot pins 99 (See FIGS. 5, 6, and 13) extending through the legs of U-shaped hinge brackets 100 secured adjacent the ends of horizontal bus bar portions 92A, 92B and 92C pivotally mount the vertically extending copper terminal bars 45 which abut against the ferrules 46 on currentlimiting fuses 39. The terminal bars 45 are electrically connected to horizontal bus bar portions 92A, 92B and 92C by flexible copper straps 101.

The insulating rods 49 are operatively connected by radial pins 104 (See FIG. 14) to U-shaped metal brackets 105 carrying insulating shoes 106 which abut against copper terminal bars 45. The terminal bars 45 fall to an inclined position shown in dot-dash lines in FIG. 13 when the fuse drawers 54 are removed, and the insulating shoes 106 extend downward through apertures 107 and 108 in fixed trays 96 and movable fuse trays 48 respectively and actuate the terminal bar 45 upward into engagement with ferrule 46 on current-limiting fuse 39 when fuse drawers 54 are again inserted into housing 22. After a fuse drawer 54 is locked to housing 22 by latch 66,

hand knob 60 on threaded shaft 58 is then turned until compression spring 64 exerts pressure against insulating shoe 106 and resiliently clamps current-limiting fuse 39 between copper terminal bar 45 and terminal means 37 on transformer-insulating bushing 36.

Terminal means 37 have circular metallic movable contacts 103 (See FIGS. 1820) which abut against the ferrules 38 on current-limiting fuses '39 and have limited universal motion relative to the transformer insulating bushings 36 and provide high current carrying engagement with the ferrules 38 even when fuses 39 are not in exact axial alignment with bushings 36. Conductive studs 109 extending axially from the porcelain insulator members 110 of transformer-insulating bushings 36 protrude into axial bores 112 in the movable contacts 103 with a relatively loose fit and are affixed thereto by pins 113 extending radially through arcuate ear portions 115 on movable contacts 103 and extending with a loose fit through an aperture in conductive stud 109, and such loose fit permits limited movement of contacts 103 in two mutually perpendicular directions relative to studs 109. A flexible current transfer copper lead 116 extends through a radial aperture 117 in stud 109, and the ends of flexible lead 116 are bent into loops and secured by suitable means such as silver solder within apertures 118 in movable contact 103 extending parallel to the axis thereof.

Leveling screws 119 (See FIG. 2) may be provided between the bottom wall of housing 22 and the structural iron channels 23 of the housing base to permit leveling of housing 22 and alignment thereof with the transformer casing 35. Short horizontal guide lugs 120 (See FIGS. 3 and 6) welded in a triangular arrangement on transformer casing 35 fit within annular collars 121 affixed on the rear wall 122 of housing 22 to align the transformer bushing terminals 37 with the fuse ferrules 38. Threaded studs 123 on the rear wall 122 of housing 22 protrude through apertures 124 in metallic plates 125 welded to transformer casing 35, and nuts are threaded on the studs 123 to affix transformer casing 35 to housing 22. Cylindrical aligning members 126 disposed within the apertures 124 have oblong axial openings 127 therein (shown in dotted lines in FIG. 3) which receive the studs 123 and are manually rotatable within the apertures 124 to align the studs 123 on housing 22 with the apertures 124 in plates 125. Transformer bushings 36 protrude from a rectangular-in-cross section recess 135 in transformer casing 35, and a gasket 136 (see FIG. 18) may be disposed between the rear wall 122 of housing 22 and the portion of transformer casing 35 defining the recess 135 to prevent entry of dust into housing 22.

The primary voltage, air break circuit breakers 26 and 27 may be commercially available three-phase, three-pole. single-throw 600 ampere load break switches rated at 13.2 kilovolts, 40,000 amperes symmetrical make and latch, and 60,000 amperes momentary, and sold under the marks ISOLATOR and ISO-QUENSOR. The specific switches do not constitute a part of the present invention and are shown somewhat schematically in FIG. 21 as including three movable tubular porcelain members 137 each of which encloses a first tulip-type contact 138 adapted to maintain continuous engagement with an axially extending bayonet contact 128 supported on insulating bushing 29 as porcelain members 137 are reciprocated axially and a second tuliptype contact 129 elecjtrically connected to contact 138 and adapted to engage and disengage a bayonet-type contact 130 mounted on insulating bushing 28. The porcelain members 137 are reciprocated axially between open and closed position by a spring-type stored energy operator 132, shown only in block form, when "a switch-operating shaft 132A or 1328 is rotated by manual movement of switch-operating handle 32A or 328.

The switch-operating shafts 132A and 1328 for circuit breakers 26 and 27 carry eccentric cams 140A and 1408 (See FIGS. 6 and 7) respectively interior of housing 22. Cam followers 141A and 1418 affixed to elongated cam follower rods 142 are urged into continuous engagement with cams 140A and .1408 by compression springs 144 which abut at one end against brackets 145 afi'rxed to housing front wall 56 (See FIGS. 7 and and at their opposite end against washers 147 disposed against pins 148 protruding through the rods 142. The cam follower rods 142 protrude through keyhole slots 150 (See FIG. 8) in a vertical, elongated, longitudinally reciprocable interlocking bar 152. Horizontal pins 153 affixed to the interior of. housing wall 56 and extending through elongated slots 155 in interlocking bar 152 guide the bar 152 as it reciprocates longitudinally and interlocking bar 152 is normally resiliently urged to its lowermost position, corresponding to the open position of both circuit breakers 26 and 27, by a compression spring 157. Spring 157 surrounds a belt 158 which slidably extends through an aperture in a horizontal portion 160 at the lower extremity of interlocking bar 152, and the head of bolt 158 abuts against a bracket 159 secured to the front wall 56 of housing 22 to prevent movement of bolt 158. Compression spring 157 abuts at one end against a nut threaded on bolt 158 and at the opposite end against horizontal portion 160 of interlocking bar 152 and urges interlocking bar 152 to its lowennost position.

Cam followers 141 have internally threaded cylindrical portions which receives bolts that bear against the cams to permit adjustment of the interlock. The cylindrical portions of the cam followers 141A and 1418 are of larger diameter than elongated rods 14,2 and can protrude through the circular portion of the keyhole slots but cannot protrude through the elongated portion of the keyhole slots 150. The portions of eccentric cams 140A and 1403 of smallest diameter engage the cam followers 141A and 1418 when circuit breakers 26 and 27 are in the open position, at which time the springs 144 urge cam followers 141 against cams 140A and 1403 so that the cam followers 141 are not within the keyhole slots 150, thereby permitting interlocking bar 152 to be moved vertically upward to allow withdrawal of fuse drawers 54 and fuses 39 from housing 22 as hereinafter described. When either circuit breaker 26 or 27 is closed to electrically connect a high-voltage tap cable 20 or 21 through fuses 39 to transformer 10, the largest diameter portion of the eccentric cams 140A or 1408 engages the corresponding cam follower 141A or 1418 and pushes it through the circular portion of the associated keyhole slot 150, thereby interfering with upward movement of interlocking bar 152 and preventing withdrawal of fuse drawers 54 from housing 22.

The air terminal chamber of the invention also has interlocking means to prevent simultaneous closing of both circuit breakers 26 and 27, thereby assuring that one high-voltage tap cable 20 is never directly connected to the other high-voltage tap cable 21. At the end opposite the cam followers 141, each of the elongated rods 142 has an axially spaced pair of pins 162 extending therethrough disposed on opposite sides of a vertical rocking" bar 163 whose midpoint is positioned adjacent a stop pin, or defeater" pin 164 afi'lxed to front wall 56 of housing 22. The pins 162 operatively connect elongated cam follower rods 142 to rocking bar 163 while permitting pivotal movement therebetween, and defeater pin 164 allows rocking bar 163 to pivot when one end thereof is moved by an elongated rod 142, but defeater pin 164 interferes with and prevents translation of rocking bar 163 transverse toits axis. When either switch-operating handle 32A or 328 is actuated to closed position, thereby rotating the corresponding eccentric cam 140A or 1408 and actuating the associated cam follower 141A or 1418 and cam follower rod 142 longitudinally,

the rocking bar 163 pivots about defeater pin 164. The other switch-operating handle 32A or 328 cannot be operated to,

closed position thereafter because the defeater pin 164 inter feres with translation of rocking bar 163 transverse to its axis, thereby preventing longitudinal reciprocation of the other cam follower rod 142 and obstructing movement of the as sociated eccentric cam 140A or 1408. It will thus be appreciated that rocking bar 163 and defeater pin 164 block simultaneous closing of both circuit breakers 26 and 27 and thus positively prevents accidental connection of one primary tap cable 20 or 21 to the other.

I Defeater pin 164 extends through an aperture in housing front wall 56 and has a head which is resiliently urged against a cup-shaped projection 166 on wall 56 by a compression spring 167 (See FIG. 9). The compression spring 167 abuts at one- 166 and at its other end against a washer 168 disposed against a pin extending through defeater pin 164, and compression spring 167 normally urges defeater pin 164 to the position shown in FIGS. 7, 9 and 10 where it obstructs translation of rocking bar 163 transverse to its length, thereby preventing simultaneous movement of both switch-operating handles 32A and 32B simultaneously to the closed position. If it is desired to simultaneously close both circuit breakers 26 and 27, defeater pin 164 is manually pulled against the force of compression spring 167 until defeater pin 164 no longer interferes with transverse translation of rocking bar 163, thereby permitting both cam follower rods 142 to move longitudinally and allowing both eccentric cams 140A and 1408 to rotate to the position wherein the largest diameter portion thereof engages the cam followers 141A and 14113.

Rocking bar 163 is normally disposed within a notch 169 in the end of defeater pin 1.64 (See FIG. 9). When defeater pin 164i is manually pulled out and both switch handles 32A and 32B are moved to closed position, rocking bar 163 is trans lated transversely and the end of defeater pin 164 rests against the rocking bar 163. When one switch handle 32A or 328 is now moved toward open position, the rocking bar 163 is again translated transversely, and defeater pin 164 is urged by spring 167 to the normal position shown in FIG. 9 wherein rocking bar 163 is within notch 169, thereby preventing return of the switch to closed position and requiring that the switch be actuated to open position.

Notch 169 presents a fiat surface to rocking bar 163 which minimizes the angular movement of rocking bar 163 when one switch handle 32 is moved between open and closed position, thereby assuring that the cam followers 141 are properly located relative to the keyhole slots 150 in interlocking bar 152 and making the interlock more positive.

The upper end of interlocking bar 152 is affixed to the connecting rod 170 of a linkage having three parallel crank arms 172 each of which is pivotally connected to one end of a crank 1174. The cranks 174 are affixed to shafts 176 which rotatably protrude through housing front wall 56 and through sleeve bearings l78'aflixed to wall 56. Exterior of housing 22. the shafts 176 are secured to the interfering arms 73 which are normally disposed horizontally in front of hand knobs 60 and thus prevent withdrawal of fuse trays 54 from housing 22. One interfering arm 73 is provided with a handle 181 (See FIGS. 3, 7 and 10) which permits manual rotation of the interfering arms 73 (which are mechanically ganged through connecting rod 170) from the solid-line horizontal position shown in FIG. 2, where they obstruct unthreading of hand knobs 60, to the vertical dot-dash line position shown in FIG. 2 wherein the hand knobs 60 can be rotated to turn the threaded shafts 58 (See FIGS. 13 and 14) in the internally threaded openings 59 in rectangular covers 53, thereby longitudinally translating the insulating rods 49 to release the pressure of springs 64 against current-limiting fuses 39 and moving hand knobs 60 to the dot-dash line position shown in FIGS. 14 and 17 where the fuse drawer latches 66 can be lifted (to the dot-dash line position shown in FIG. 17) to remove the ears 67 from behind the hook-shaped catches 70, thereby permitting withdrawal of fuse drawers 54 from housing 22 (to the dash-dot line position shown in FIG. 6).

A bolt 185 threaded through a bracket 186 (See FIGS. 2 and 3) on housing front wall 56 normally interferes with one of the ganged interfering arms 73 and prevents movement thereof from the horizontal position shown in full lines in FIG. 2, where they interfere with outward movement of hand knobs 60, to the vertical position shown in dot-dash lines wherein hand knobs 60 can be rotated to free the fuse drawer latches 66 so that fuse drawers 54 can be withdrawn from housing 22 as seen in FIG. 6. When fuse drawers 54 are closed and interfering'arms 73 are in their normal horizontal position, the linkage of parallel crank arms 172 and connecting rod 170 is in the uppermost position shown in full lines in FIG. 7, thereby' raising interlocking bar 152 to its uppermost position wherein the circular portion of keyhole slots 150 are opposite the cam &

followers 141A and 1413. It will be appreciated that in this horizontal position of interfering arms 73 and uppermost position of interlocking bar 152, the eccentric cams A and 1408 can be rotated to push 'the cam followers 141A and 1418 through the keyhole slots 150, and consequently one switch actuating arm 32A or 328 can be rotated from open to closed position to close the corresponding circuit breaker 26 or 27 and connect one high-voltage tap cable 20 or 21 through fuses 39 to transformer 10. When either circuit breaker 26 or 27 is closed, the associated cam follower 141A or 1418 protrudes through the circular portion of a keyhole slot 150, thereby obstructing downward movement of interlocking bar 152, preventing movement of linkage including crank arms 172, obstructing rotation of interfering arms 73 and preventing withdrawal of fuse drawers 54 from housing 22 as long as one circuit breaker 26 or 27 is closed. When the circuit breaker is opened, the associated cam follower 141A or 1413 is removed from the keyhole slot 150, the interlocking bar 152 can be lowered because the cam follower rods 142 slide in the elongated portion of the keyhole slots 15 D, and interfering arms 73 can be rotated by means of handle 181 to lower the linkage to the lowermost position shown in dot-dash lines in FIG. 7, thereby permitting unthreading of hand knobs 60 and withdrawal of fuse drawers 54 from housing 22 and also interfering with movement of either circuit breaker 26 or 27 to the closed position by the elongated portion of keyhole slots preventing longitudinal movement of cam followers 141A and 1418.

While only a single embodiment of the invention has been illustrated and described, many modifications and variations thereof will be readily apparent to those skilled in the art, and consequently it is intended in the appended claims to cover all such modifications and variations thereof which are within the true spirit and scope of the invention.

We claim:

1. In an indoor power center, the combination of:

a housing,

a first polyphase high-voltage circuit interrupter within said housing operable between open and closed positions and having phase output terminals and also having phase input terminals adapted to be connected to a first highvoltage electrical cable,

a second polyphase high-voltage circuit interrupter within said housing operable between open and closed positions independently of said first circuit interrupter and having phase output terminals and also having phase input terminals adapted to be connected to a second high-voltage electrical cable,

a plurality of fuse drawers reciprocable into and out of said housing,

an elongated fuse positioned on each said fuse drawer,

a movable connector member for each said fuse drawer engaging one end of said fuse on said fuse drawer when said fuse drawer is inserted into said housing and being electrically connected to corresponding phase output terminals of both said first and said second circuit interrupters,

means on each said fuse drawer operable from the exterior of said housing, when said fuse drawer is inserted within said housing, for resiliently urging said connector member against said one end of said fuse on said fuse drawer, and

interlock means for preventing withdrawal of said fuse drawers from said housing when either said first or said second circuit interrupter is in closed position.

2. In the combination defined by claim 1 wherein said interlock means includes means for preventing operation of either of said circuit interrupters to closed position when said fuse drawers can be withdrawn from said housing.

3. In the combination defined by claim 1 wherein said interlock means also includes means for preventing simultaneous operation of both of said circuit interrupters to closed position.

4. ln the combination defined by claim 1 wherein said housing has an opening therein through which the opposite end of said fuses are exposed and also including an electric transfonner having a plurality of insulating bushings in said common plane and in alignment with said fuses provided with terminal means protruding through said opening in said housing into electrical engagement with said opposite end of said fuses.

5. In the combination defined by claim I wherein said first and second circuit interrupters have casings disposed back-toback in horizontal planes adjacent the bottom of said housing and said common plane in which said fuse drawers are disposed is horizontal and above said circuit interrupter casmgs.

6. In the combination defined by claim 5 wherein said circuit interrupters arethree phase and each of said circuit interrupters has three poles and three insulating bushings extending horizontally from each end thereof carrying said input and output terminals, and also including means for electrically commoning corresponding phase output terminals of said pair of circuit interrupters and electrically connecting them to one of said connector members.

7. In the combination defined by claim 4 wherein said connector members are pivoted metallic bars and including fuseclamping means on each said fuse drawer operable from the exterior of said housing, when said fuse drawers are inserted into said housing, for resiliently urging saidconnector member against said one end of said fuse to thereby push said opposite end against said terminal means on said transformer insulating bushing, and means for latching said fuse drawers to said hous- 8. In the combination defined by claim 7 wherein said fuse drawer latching means includes a latching member on each fuse drawer movable between a latching position wherein said fuse drawer is held against withdrawal from said housing and a released position wherein said drawer may be withdrawn and wherein said fuse-clamping means interferes with and holds said latching member in said latching position when said fuse is clamped against said terminal means on said insulating bushing.

9. In the combination defined by claim 7 wherein said interlock means includes means to prevent operation of said fuseclamping means in a direction to remove clamping pressure on said fuses when either of said circuit interrupters is in closed position.

10. In the combination defined by claim 4 and including means for providing universal motion of said terminal means on said transfonner insulating bushings relative to said bushings and for simultaneously maintaining continuous electrical connection between said fuses and said transformer, whereby said terminal means are in current transfer relation with said fuses even when said bushings and fuses are slightly misaligned.

11. In the combination defined by claim 7 wherein said housing has a plurality of stationary insulating trays positioned in a horizontal plane above said circuit interrupters and said fuse drawers are supported on and slidable along said trays.

12. In the combination defined by claim 11 wherein said stationary trays are supported on vertical standoff insulators and said trays and fuse drawers have registering apertures therein when said fuse drawers are inserted into said housing and said pivoted connector members protrude through said registering apertures into engagement with said one end of said fuses.

13. In the combination defined by claim 6 wherein said means for electrically commoning includes a plurality of bus bars having vertical portions electrically commoning corresponding phase output terminals of said pair of circuit interrupters and horizontal portions disposed above said circuit interrupters and said connector members are pivotally mounted and electrically connected to and supported on said horizontal portions of said bus bars.

14. In the combination of claim 8 wherein each said fuseclamping means includes rotatable threaded means on each said fuse drawer having a manual knob accessible from the exterior of said housing for engaging said pivoted connector member and actuating it in a direction longitudinally of said drawer to urge said other end of said fuse against said terminal means on said insulating bushing, and wherein said manual knob holds said latching member in said latching position when said fuse is clamped against said terminal means.

15. In the combination defined by claim 14 wherein said fuse-clamping means includes an elongated insulating rod on each fuse drawer having one end disposed adjacent said connector member when said drawer is inserted into said housing, means including a rotatable threaded member accessible from the exterior of said housing for actuating said rod longitudinally to push said connector member against said one end of said fuse, and spring means disposed between said insulating rod and said threaded member.

16. In the combination defined by claim 15 wherein each of said' fuse drawers has a vertical front wall disposed against said housing when'said drawer is closed and having a tapped opening therein and said rotatable member of said fuse-clamping means is a threaded shaft engaged within said opening and having a manual knob integral therewith exterior of said housing, and wherein said manual knob holds said latching member against moti'on when said fuse is clamped against said terminal means, whereby said fuse drawer cannot be withdrawn from said housing until said threaded shaft is rotated sufficiently to remove the'clamping pressure on said fuse.

17. In the combination defined by claim 16 wherein said interlock means for preventing withdrawal of said fuse drawers from said housing when either of said circuit interrupters isin closed position includes a plurality of mechanically ganged interfering arms rotatably mounted about parallel axes on said housing and being rotatable between an interfering position wherein they block rotation of said manual knob and also obstruct withdrawal of said drawers from said housing and a noninterfering position wherein said manual knob and threaded shaft can be rotated and said fuse drawers can be withdrawn from said housing.

18. In the combination defined by claim 16 wherein each said means for latching said fuse drawer to said housing includes an eye on the front wall of said fuse drawer, a hook portion on said housing, and a latch member having an ear extending through said eye and engageable with said hook portion when said drawer is inserted into said housing, and

wherein said threaded shaft is rotatable in a direction to urge said connector member against said fuse and to a position wherein said manual knob holds said latch member against motion and prevents removal of said ear from said hook portion, whereby said fuse drawer cannot be withdrawn from said housing until both said circuit interrupters are open and said fuse-clamping means is released.

I9. In the combination defined by claim 1 wherein each said circuit interrupter is actuated between open and closed positions by a rotatable operating member and said interlock means includes a rotatable cam operatively connected to each said operating member, a cam follower engaging each said cam and contacting a limit position thereof when the corresponding circuit interrupter is closed, and means responsive to either cam follower engaging said limit position of the corresponding cam for interfering with removal of said fuse drawers from said housing.

20. ln the combination defined by claim 19 wherein said means for interfering with removal of said fuse drawers includes a plurality of mechanically ganged interfering arms each of which is rotatable to an interfering position wherein it is in front of and blocks withdrawal of one of said fuse drawers from said housing.

21. In the combination defined by claim 19 wherein said cam followers are rods disposed generally parallel to each other and adapted to be translated longitudinally by said cams and said means for preventing simultaneous operation of both of said circuit interrupters to closed position includes an elongated rocker bar disposed transverse to and operatively connected adjacent its ends to said cam follower rods and a stationary stop disposed adjacent said rocker bar intermediate its ends and positioned to permit pivotal movement of said rocker bar about said stop, when one cam follower rod is moved longitudinally, but to interfere with transverse translation of said rocker bar when both said cams are rotated in a direction to actuate said cam follower rods longitudinally.

22. in the combination defined by claim 21 wherein said stop member is a defeater pin manually retractable to a noninterfering position wherein said rocker bar can be transversely translated, thereby permitting both of said circuit interrupters to be operated to the closed position when desired.

23. In the combination defined by claim wherein each said cam follower has an enlarged diameter portion and said cam followers are adapted to be translated longitudinally by said cams and said means for preventing operation of either circuit interrupter to closed position when said fuse drawers can be withdrawn from said housing includes a reciprocable interlocking bar having keyhole openings therein through each of which one of said cam followers extends, the circular portion of each said keyhole opening being adapted to receive said enlarged diameter portion of said cam follower and said enlarged diameter being greater than the width of the rectangular portion of said keyhole opening, whereby said interlocking bar cannot be reciprocated when one of said cams has been rotated to actuate said enlarged diameter portion of the corresponding cam follower into said circular portion of said keyhole opening and said cam cannot be rotated to close said circuit interrupters when the cam followers are within said rectangular portion of said keyhole openings.

24. in the combination defined by claim 23 wherein said interfering arms are manually rotatable and including parallel crank linkage means operatively connecting said reciprocable interlocking bar and said mechanically ganged interfering arms for reciprocating said interlocking bar to a position wherein said cam followers are within said rectangular portions of said keyhole openings when said interfering arms are rotated to a noninterfering position wherein said fuse drawers may be withdrawn from said housing, whereby said circuit interrupters cannot be closed when said fuse drawers can be withdrawn from said housing.

25. In the combination defined by claim 24 wherein said parallel crank linkage means is responsive to rotation of said interfering arms to the interfering position wherein they block withdrawal of said fuse drawers from said housing to reciprocate said interlocking bar to the position wherein said cam followers are within said circular portion of said keyhole openings, whereby one of said circuit .interrupters can be closed when said interfering arms prevent withdrawal of said drawers and said interfering arms cannot be rotated to permit fuse drawer withdrawal after one of said operating members is rotated to close the corresponding circuit interrupter and move said enlarged diameter portion of the cam follower into the circular portion of the keyhole opening. 7

26. In the combination defined by claim 1 wherein each of said circuit interrupters is actuated between open and closed position by a rotatable operating member and said means for preventing simultaneous operation of both circuit interrupters to closed position has associated with each said circuit interrupter a rotary cam operatively connected to said rotatable operating member, a cam follower rod associated with said cam and engaging a limit position thereon when said circuit interrupter is in closed position, spring means for resiliently urging said cam follower rod into engagement with said cam, and means including an elongated rocking bar operatively connected to said cam follower rods at its opposite ends and a stationary stop member adjacent the middle and interfering with transverse translation of said elongated bar for preventing simultaneous rotation of both of said eccentric cams to the position wherein said limit position thereon engages said cam follower rod.

27. ln the combination defined by claim 26 wherein said cam follower rods have an enlarged diameter portion and said means for preventing withdrawal of said drawers from said housing includes a plurality of mechanically ganged interference arms rotatable about parallel axes between an interfering position wherein they interfere with withdrawal, of said drawers from said housing and a noninterfering position wherein said drawers can be withdrawn, and means including an elongated reciprocable interlocking bar operatively connected to said ganged interfering arms and having keyhole openings therein receiving said cam follower rods and being responsive to said interfering arms being in said interfering position for preventing rotation of either of said cams to the position wherein its associated cam follower rod engages said limit position of said cam.

28. In the combination defined by claim 27 wherein said means for preventing rotation of either of said cams includes parallel bar linkage means operatively connected to said ganged interference arms for reciprocating said interlocking bar between a first position wherein said cam follower rods are in the circular portion of said keyhole openings when said interfering arms are in said interfering position and a second position wherein said cam follower rods are in the rectangular portion of said keyhole openings when said interfering arms are in said noninterfering position, whereby one of said operating members can be rotated to close the corresponding circuit interrupter and actuate said enlarged diameter portion of said cam follower rod into said circular portion of said keyhole opening when said interfering arms are in said interfering position, thereby preventing movement of said interfering arms to the noninterfering position when one of said circuit interrupters is closed.

29. ln the combination defined by claim 4 wherein said electrical transformer has a casing adjacent said housing and including three mating male and female means positioned at the vertices of a'triangle for aligning said transformer casing with said housing, each said aligning means comprising a stud member and a ring member slidably receiving said stud member, one of said members being affixed to said housing and the other being affixed to said casing.

30. In the combination defined by claim 4 wherein said electrical transformer has a casing adjacent said housing and including a plurality of means for securing said casing to said housing, each of said securing means including a threaded stud member, a plate member having a circular aperture therein, a cylindrical alignment compensating member disposed and adapted to rotate within said circular aperture and having an oblong axial opening receiving said threaded stud member, one of said members being affixed to said casing and the other being affixed to said housing.

31. in the combination defined by claim 2 wherein said interlock means also includes means for preventing simultaneous operation of both of said circuit interrupters to closed position and said housing has an opening therein through which the opposite ends of said fuses are exposed and also including an electrical transformer having a plurality of insulating bushings in said common plane and in alignment with said fuses provided with terminal means protruding through said opening in said housing into electrical engagement with said opposite end of said fuses.

32. In the combination defined by claim 31 wherein said circuit interrupters have casings disposed back-to-back in horizontal planes adjacent the bottom of said housing and said common plane, in which 'said fuse drawers is disposed, is horizontal and above said circuit interrupter casings and said circuit interrupters and said transformer are three phase and each said circuit interrupter has three poles and three insulating bushings extending horizontally from each end thereof carrying input and output terminals, and also including means for electrically commoning corresponding phase output terminals of said pair of circuit interrupters and electrically connecting them to one of said connector members.

33. in the combination defined by claim 31 wherein said connector members are pivoted metallic bars and including fuse-clamping means on each said fuse drawer operable from the exterior of said housing, when said fuse drawers are inserted into said housing, for resiliently urging said connector member against said one end of said fuse to thereby push said opposite end against said terminal means on said transformerinsulating bushings, and means for latching said fuse drawers to said housing.

34. In the combination defined by claim 7 wherein said fuse drawer latching means includes a latching member on each fuse drawer movable between a latching position wherein said fuse drawer is held against withdrawal from said housing and a released position wherein said drawer may be withdrawn and wherein said fuse-clamping means interferes with and holds said latching member in said latching position when said fuse is clamped against said terminal means on said insulating bushing and wherein said interlock means includes means to prevent operation of said fuse-clamping means in a direction to remove clamping pressure on said fuses when either of said circuit interrupters is in closed position.

35. In the combination defined by claim 33 wherein said fuse drawer latching means includes a latching member on each fuse drawer movable between a latching position wherein said fuse drawer is held against withdrawal from said housing and a released position wherein said drawer may be withdrawn and wherein said fuse-clamping means interferes with and holds said latching member in said latching position when said fuse is clamped against said tenninal means on said insulating bushing and wherein said interlock means includes means to prevent operation of said fuse-clamping means in a direction to remove clamping pressure on said fuses when either of said circuit interrupters is in closed position.

36. In the combination defined by claim 34 and including means for providing universal motion of said terminal means on said transformer-insulating bushings relative to said bushings and for simultaneously maintaining continuous electrical connection between said fuses and said transformer, whereby said terminal means are in current transfer relation with said fuses even when said bushings and fuses are slightly misaligned.

37. In the combination defined by claim 8 wherein said housing has a plurality of stationary insulating trays positioned in a horizontal plane above said circuit interrupters and supported on vertical standoff insulators and said fuse drawers are supported on and slidable along said trays and said trays and fuse drawers have registering apertures therein, when said fuse drawers are inserted into said housing, and said pivoted connector members protrude through said registering apertures into engagement with said one end of said fuses.

38. In the combination defined by claim 12 and also including means for electrically commoning corresponding phase output terminals of said pair of circuit interrupters and electrically connecting them to one of said connector members and wherein said means for electrically commoning includes a plurality of bus bars having vertical portions electrically commoning corresponding phase output terminals of said first and second circuit interrupters and horizontal portions disposed above said circuit interrupters and said connector members are pivotally mounted and electrically connected to and supported on said horizontal portions of said bus bars.

39. In the combination defined by claim 38 wherein each said fuse-clamping means includes rotatable threaded means on each said fuse drawer having a manual knob accessible from the exterior of said housing for engaging said pivoted connector member and actuating it.in a direction longitudinally of said drawer to urge said other end of said fuse against said terminal means on said insulating bushing, and wherein said manual knob holds said latching member in said latching position when said fuse is clamped against said terminal means and said fuse-clamping means includes an elongated insulating rod on each fuse drawer having one end disposed adjacent said connector member when said drawer is inserted into said housing, means including a rotatable threaded member accessible from the exterior of said housing for actuating said rod longitudinally to push said connector member against said one end of said fuse, and spring means disposed between said insulating rod and said threaded member.

40. In the combination defined by claim 17 wherein each said fuse means for latching said fuse drawer to said housing includes an eye on the front wall of said fuse drawer, a hook portion on said housing, and a latch member having an ear extending through said eye and engageable with said hook portion when said drawer is inserted into said housing, and wherein said threaded shaft is rotatable in a direction to urge said connector member against said fuse and to a position wherein said manual knob holds said latch member against motion and prevents removal of said ear from said hook portion, whereby said fuse drawer cannot be withdrawn from housing until both said circuit interrupters are open and said fuse-clamping means is released.

41. In the combination defined by claim 31 wherein each said circuit interrupter is actuated between open and closed positions by a rotatable operating member and said interlock means includes a rotatable cam operatively connected to each said operating member, a cam follower engaging each said cam and contacting a limit position thereof when the corresponding circuit interrupter is closed, and means responsive to either cam follower engaging said limit position of the corresponding cam for interfering with removal of said fuse drawers from said housing including a plurality of mechanically ganged interfering arms each of which is rotatable to an interfering position wherein it blocks removal of one of said fuse drawers from said housing.

42. In the combination defined by claim 41 wherein said connector members are pivoted metallic bars and including fuse-clamping means on each said fuse drawer operable from the exterior of said housing, when said fuse drawers are inserted into said housing, for resiliently urging said connector member against said one end of said fuse to thereby push said opposite end against said terminal means on said transformer.- insulating bushing, means for latching said fuse drawers to said housing, and wherein said interlock means includes means to prevent operation of said fuse-clamping means in a direction to remove clamping pressure on said fuses when either of said circuit interrupters is in closed position.

43. In the combination defined by claim 42 wherein said means for interfering with removal of said fuse drawers includes a plurality of mechanically ganged interfering anns each of which is rotatable to an interfering position wherein it blocks withdrawal of one of said fuse drawers from said housing and said cam followers are generally parallel rods adapted to be translated longitudinally by said cams and said means for preventing simultaneous operation of both of said circuit interrupters to closed position includes an elongated rocker bar disposed transverse to and operatively connected adjacent its ends to said cam follower rods and a stationary stop disposed adjacent said rocker bar intermediate its ends and positioned to permit pivotal movement of said rocker bar about said stop, when one cam follower rod is moved longitudinally, but to interfere with transverse translation of said rocker bar when both said cams are rotated in a direction to actuate said cam follower rods longitudinally.

44. In the combination defined by claim 25 wherein said cam followers are generally parallel rods adapted to be translated longitudinally by said cams and said means for preventing simultaneous operation of both of said circuit interrupters to closed position includes an elongated rocker bar disposed transverse to and operatively connected adjacentits ends to said cam follower rods and a stationary stop disposed adjacent said rocker bar intermediate its ends and positioned to permit pivotal movement of said rocker bar about said stop, when one cam follower rod is moved longitudinally, but to interfere with transverse translation of said rocker bar when both cams are rotated in a direction to actuate said cam follower rods longitudinally.

45. ln the combination defined by claim 33 wherein each of said circuit interrupters is actuated between open and closed positions by a rotatable operating member and said means for preventing simultaneous operation of both circuit interrupters to closed position has associated with each said circuit interrupter a rotary cam operatively connected to said rotatable operating member, a cam follower rod associated with said cam and engaging a limit position thereon when said circuit interrupter is in closed position, and means including an elongated rocking bar operatively connected to said cam follower rods at its opposite ends and a stationary stop member adjacent the middle and interfering with transverse translation of said elongated bar for preventing simultaneous rotation of both said eccentric cams to the position wherein said limit position thereon engages said cam follower rod.

46. In the combination defined by claim 11 and including latching means oneach said fuse drawer movable between a latching position wherein said fuse drawer is held against withdrawal from said housing and a released position wherein said drawer may be withdrawn and wherein said means for urging said connector member against one end of said fuse interferes with and holds said latching means in said latching position,

47. in the combination defined by claim 46 wherein said interlock means includes means to prevent release of said means for urging said connector member against one end of said fuse when either said first or said second circuit interrupter is in closed position.

48. In the combination defined by claim 47 wherein said housing has a plurality of stationary trays positioned in a horizontal plane and said fuse drawers are supported on and slidable on said trays, and wherein said trays and fuse drawers have registering apertures therein, when said fuse drawers are inserted into said housing, and said connector members protrude through said registering apertures into engagement with said one end of said fuses.

49. in combination,

a housing,

a high-voltage circuit interrupter within said housing operable between open and closed positions and having an output terminal and also having an input terminal adapted to be connected to a high-voltage electrical cable,

a fuse drawer reciprocable into and out of said housing.

an elongated fuse on each said fuse drawer,

a movable connector member engaging one end of said fuse on said fuse drawer, when said fuse drawer is inserted into said housing, and being electrically connected to said output terminal,

means for latching said fuse drawer to said housing, and

fuse-clamping means on said fuse drawer operable from the exterior of said housing, when said fuse drawer is inserted into said housing, for urging said connector member against one end of said fuse,

said fuse-clamping means interfering with and preventing release of said drawer-latching means when said connector member is urged against said one end of said fuse.

S0. in the combination defined by claim 49 and including interlock means for preventing operation of said fuse-clamping means in a direction to permit said connector member to disengage said one end of said fuse when said circuit interrupter is'in closed position.

51. In the combination defined by claim 50 wherein said housing has a stationary tray and said fuse drawer is supported on and slidable on said tray and wherein said tray and fuse drawer have registering apertures, when said fuse drawer is inserted into said housing, and said connector member is pivoted and protrudes through said registering apertures into engagement with said one end of said fuse.

52. In the combination defined by claim 50 wherein said connector member is pivoted and said means for latching said fuse'drawerincludes a latching member on said fuse drawer movable between a latching position wherein said fuse drawer is held against withdrawal from said housing and a released position wherein said drawer ma be withdrawn and said fuseclamping means includes rotata le threaded means on said fuse drawer having a manual knob accessible from the exterior of said housing for engaging said pivoted connector member and actuating it in a direction longitudinally of said drawer and against said one end of said fuse, and wherein said manual knob holds said latching member in said latching position when said connector member is urged against said one end of said fuse.

53. In the combination defined by claim 52 and including interlock means for preventing withdrawal of said fuse drawer from said housing when said circuit interrupter is closed.

54. In the combination defined by claim 53 wherein said interlock means includes an interfering arm mounted on said housing for rotation between an interfering position wherein it blocks rotation of said manual knob and withdrawal of said fuse drawer from said housing when said circuit interrupter is closed and a noninterfering position wherein said manual knob and said threaded means can be rotated until said pivoted connector member disengages said one end of said fuse and said latching member can be moved to said released position.

55. In the combination defined by claim 54 wherein said fuse drawer has an aperture therein and said fuse-clamping means includes an elongated insulating rod on said fuse drawer movable longitudinally thereof, an insulating shoe disposed adjacent one end of said insulating rod and depending through said aperture in said drawer and being adapted to engage said connector member and pivot it upwards against said one end of said fuse when said drawer is inserted into said housing, and spring means disposed between and operatively connecting said rotatable threaded means and said insulating rod. 

1. In an indoor power center, the combination of: a housing, a first polyphase high-voltage circuit interrupter within said housing operable between open and closed positions and having phase output terminals and also having phase input terminals adapted to be connected to a first high-voltage electrical cable, a second polyphase high-voltage circuit interrupter within said housing operable between open and closed positions independently of said first circuit interrupter and having phase output terminals and also having phase input terminals adapted to be connected to a second high-voltage electrical cable, a plurality of fuse drawers reciprocable into and out of said housing, an elongated fuse positioned on each said fuse drawer, a movable connector member for each said fuse drawer engaging one end of said fuse on said fuse drawer when said fuse drawer is inserted into said housing and being electrically connected to corresponding phase output terminals of both said first and said second circuit interrupters, means on each said fuse drawer operable from the exterior of said housing, when said fuse drawer is inserted within said housing, for resiliently urging said connector member against said one end of said fuse on said fuse drawer, and interlock means for preventing withdrawal of said fuse drawers from said housing when either said first or said second circuit interrupter is in closed position.
 2. In the combination defined by claim 1 wherein said interlock means includes means for preventing operation of either of said circuit interrupters to closed position when said fuse drawers can be withdrawn from said housing.
 3. In the combination defined by claim 1 wherein said interlock means also includes means for preventing simultaneous operation of both of said circuit interrupters to closed position.
 4. In the combination deFined by claim 1 wherein said housing has an opening therein through which the opposite end of said fuses are exposed and also including an electric transformer having a plurality of insulating bushings in said common plane and in alignment with said fuses provided with terminal means protruding through said opening in said housing into electrical engagement with said opposite end of said fuses.
 5. In the combination defined by claim 1 wherein said first and second circuit interrupters have casings disposed back-to-back in horizontal planes adjacent the bottom of said housing and said common plane in which said fuse drawers are disposed is horizontal and above said circuit interrupter casings.
 6. In the combination defined by claim 5 wherein said circuit interrupters are three phase and each of said circuit interrupters has three poles and three insulating bushings extending horizontally from each end thereof carrying said input and output terminals, and also including means for electrically commoning corresponding phase output terminals of said pair of circuit interrupters and electrically connecting them to one of said connector members.
 7. In the combination defined by claim 4 wherein said connector members are pivoted metallic bars and including fuse-clamping means on each said fuse drawer operable from the exterior of said housing, when said fuse drawers are inserted into said housing, for resiliently urging said connector member against said one end of said fuse to thereby push said opposite end against said terminal means on said transformer insulating bushing, and means for latching said fuse drawers to said housing.
 8. In the combination defined by claim 7 wherein said fuse drawer latching means includes a latching member on each fuse drawer movable between a latching position wherein said fuse drawer is held against withdrawal from said housing and a released position wherein said drawer may be withdrawn and wherein said fuse-clamping means interferes with and holds said latching member in said latching position when said fuse is clamped against said terminal means on said insulating bushing.
 9. In the combination defined by claim 7 wherein said interlock means includes means to prevent operation of said fuse-clamping means in a direction to remove clamping pressure on said fuses when either of said circuit interrupters is in closed position.
 10. In the combination defined by claim 4 and including means for providing universal motion of said terminal means on said transformer insulating bushings relative to said bushings and for simultaneously maintaining continuous electrical connection between said fuses and said transformer, whereby said terminal means are in current transfer relation with said fuses even when said bushings and fuses are slightly misaligned.
 11. In the combination defined by claim 7 wherein said housing has a plurality of stationary insulating trays positioned in a horizontal plane above said circuit interrupters and said fuse drawers are supported on and slidable along said trays.
 12. In the combination defined by claim 11 wherein said stationary trays are supported on vertical standoff insulators and said trays and fuse drawers have registering apertures therein when said fuse drawers are inserted into said housing and said pivoted connector members protrude through said registering apertures into engagement with said one end of said fuses.
 13. In the combination defined by claim 6 wherein said means for electrically commoning includes a plurality of bus bars having vertical portions electrically commoning corresponding phase output terminals of said pair of circuit interrupters and horizontal portions disposed above said circuit interrupters and said connector members are pivotally mounted and electrically connected to and supported on said horizontal portions of said bus bars.
 14. In the combination of claim 8 wherein each said fuse-clamping means includes rotatable threaded means on each said fuse drawer having a manual knob accessible from the exterior of said housing for engaging said pivoted connector member and actuating it in a direction longitudinally of said drawer to urge said other end of said fuse against said terminal means on said insulating bushing, and wherein said manual knob holds said latching member in said latching position when said fuse is clamped against said terminal means.
 15. In the combination defined by claim 14 wherein said fuse-clamping means includes an elongated insulating rod on each fuse drawer having one end disposed adjacent said connector member when said drawer is inserted into said housing, means including a rotatable threaded member accessible from the exterior of said housing for actuating said rod longitudinally to push said connector member against said one end of said fuse, and spring means disposed between said insulating rod and said threaded member.
 16. In the combination defined by claim 15 wherein each of said fuse drawers has a vertical front wall disposed against said housing when said drawer is closed and having a tapped opening therein and said rotatable member of said fuse-clamping means is a threaded shaft engaged within said opening and having a manual knob integral therewith exterior of said housing, and wherein said manual knob holds said latching member against motion when said fuse is clamped against said terminal means, whereby said fuse drawer cannot be withdrawn from said housing until said threaded shaft is rotated sufficiently to remove the clamping pressure on said fuse.
 17. In the combination defined by claim 16 wherein said interlock means for preventing withdrawal of said fuse drawers from said housing when either of said circuit interrupters is in closed position includes a plurality of mechanically ganged interfering arms rotatably mounted about parallel axes on said housing and being rotatable between an interfering position wherein they block rotation of said manual knob and also obstruct withdrawal of said drawers from said housing and a noninterfering position wherein said manual knob and threaded shaft can be rotated and said fuse drawers can be withdrawn from said housing.
 18. In the combination defined by claim 16 wherein each said means for latching said fuse drawer to said housing includes an eye on the front wall of said fuse drawer, a hook portion on said housing, and a latch member having an ear extending through said eye and engageable with said hook portion when said drawer is inserted into said housing, and wherein said threaded shaft is rotatable in a direction to urge said connector member against said fuse and to a position wherein said manual knob holds said latch member against motion and prevents removal of said ear from said hook portion, whereby said fuse drawer cannot be withdrawn from said housing until both said circuit interrupters are open and said fuse-clamping means is released.
 19. In the combination defined by claim 1 wherein each said circuit interrupter is actuated between open and closed positions by a rotatable operating member and said interlock means includes a rotatable cam operatively connected to each said operating member, a cam follower engaging each said cam and contacting a limit position thereof when the corresponding circuit interrupter is closed, and means responsive to either cam follower engaging said limit position of the corresponding cam for interfering with removal of said fuse drawers from said housing.
 20. In the combination defined by claim 19 wherein said means for interfering with removal of said fuse drawers includes a plurality of mechanically ganged interfering arms each of which is rotatable to an interfering position wherein it is in front of and blocks withdrawal of one of said fuse drawers from said housing.
 21. In the combination defined by claim 19 wherein said cam followers are rods disposed generally parallel to each other and adapted to be translated longitudinally by said cams and said means for preventing simultaneous operatioN of both of said circuit interrupters to closed position includes an elongated rocker bar disposed transverse to and operatively connected adjacent its ends to said cam follower rods and a stationary stop disposed adjacent said rocker bar intermediate its ends and positioned to permit pivotal movement of said rocker bar about said stop, when one cam follower rod is moved longitudinally, but to interfere with transverse translation of said rocker bar when both said cams are rotated in a direction to actuate said cam follower rods longitudinally.
 22. In the combination defined by claim 21 wherein said stop member is a defeater pin manually retractable to a noninterfering position wherein said rocker bar can be transversely translated, thereby permitting both of said circuit interrupters to be operated to the closed position when desired.
 23. In the combination defined by claim 20 wherein each said cam follower has an enlarged diameter portion and said cam followers are adapted to be translated longitudinally by said cams and said means for preventing operation of either circuit interrupter to closed position when said fuse drawers can be withdrawn from said housing includes a reciprocable interlocking bar having keyhole openings therein through each of which one of said cam followers extends, the circular portion of each said keyhole opening being adapted to receive said enlarged diameter portion of said cam follower and said enlarged diameter being greater than the width of the rectangular portion of said keyhole opening, whereby said interlocking bar cannot be reciprocated when one of said cams has been rotated to actuate said enlarged diameter portion of the corresponding cam follower into said circular portion of said keyhole opening and said cam cannot be rotated to close said circuit interrupters when the cam followers are within said rectangular portion of said keyhole openings.
 24. In the combination defined by claim 23 wherein said interfering arms are manually rotatable and including parallel crank linkage means operatively connecting said reciprocable interlocking bar and said mechanically ganged interfering arms for reciprocating said interlocking bar to a position wherein said cam followers are within said rectangular portions of said keyhole openings when said interfering arms are rotated to a noninterfering position wherein said fuse drawers may be withdrawn from said housing, whereby said circuit interrupters cannot be closed when said fuse drawers can be withdrawn from said housing.
 25. In the combination defined by claim 24 wherein said parallel crank linkage means is responsive to rotation of said interfering arms to the interfering position wherein they block withdrawal of said fuse drawers from said housing to reciprocate said interlocking bar to the position wherein said cam followers are within said circular portion of said keyhole openings, whereby one of said circuit interrupters can be closed when said interfering arms prevent withdrawal of said drawers and said interfering arms cannot be rotated to permit fuse drawer withdrawal after one of said operating members is rotated to close the corresponding circuit interrupter and move said enlarged diameter portion of the cam follower into the circular portion of the keyhole opening.
 26. In the combination defined by claim 1 wherein each of said circuit interrupters is actuated between open and closed position by a rotatable operating member and said means for preventing simultaneous operation of both circuit interrupters to closed position has associated with each said circuit interrupter a rotary cam operatively connected to said rotatable operating member, a cam follower rod associated with said cam and engaging a limit position thereon when said circuit interrupter is in closed position, spring means for resiliently urging said cam follower rod into engagement with said cam, and means including an elongated rocking bar operatively connected to said cam follower rods at its opposite ends and a Stationary stop member adjacent the middle and interfering with transverse translation of said elongated bar for preventing simultaneous rotation of both of said eccentric cams to the position wherein said limit position thereon engages said cam follower rod.
 27. In the combination defined by claim 26 wherein said cam follower rods have an enlarged diameter portion and said means for preventing withdrawal of said drawers from said housing includes a plurality of mechanically ganged interference arms rotatable about parallel axes between an interfering position wherein they interfere with withdrawal of said drawers from said housing and a noninterfering position wherein said drawers can be withdrawn, and means including an elongated reciprocable interlocking bar operatively connected to said ganged interfering arms and having keyhole openings therein receiving said cam follower rods and being responsive to said interfering arms being in said interfering position for preventing rotation of either of said cams to the position wherein its associated cam follower rod engages said limit position of said cam.
 28. In the combination defined by claim 27 wherein said means for preventing rotation of either of said cams includes parallel bar linkage means operatively connected to said ganged interference arms for reciprocating said interlocking bar between a first position wherein said cam follower rods are in the circular portion of said keyhole openings when said interfering arms are in said interfering position and a second position wherein said cam follower rods are in the rectangular portion of said keyhole openings when said interfering arms are in said noninterfering position, whereby one of said operating members can be rotated to close the corresponding circuit interrupter and actuate said enlarged diameter portion of said cam follower rod into said circular portion of said keyhole opening when said interfering arms are in said interfering position, thereby preventing movement of said interfering arms to the noninterfering position when one of said circuit interrupters is closed.
 29. In the combination defined by claim 4 wherein said electrical transformer has a casing adjacent said housing and including three mating male and female means positioned at the vertices of a triangle for aligning said transformer casing with said housing, each said aligning means comprising a stud member and a ring member slidably receiving said stud member, one of said members being affixed to said housing and the other being affixed to said casing.
 30. In the combination defined by claim 4 wherein said electrical transformer has a casing adjacent said housing and including a plurality of means for securing said casing to said housing, each of said securing means including a threaded stud member, a plate member having a circular aperture therein, a cylindrical alignment compensating member disposed and adapted to rotate within said circular aperture and having an oblong axial opening receiving said threaded stud member, one of said members being affixed to said casing and the other being affixed to said housing.
 31. In the combination defined by claim 2 wherein said interlock means also includes means for preventing simultaneous operation of both of said circuit interrupters to closed position and said housing has an opening therein through which the opposite ends of said fuses are exposed and also including an electrical transformer having a plurality of insulating bushings in said common plane and in alignment with said fuses provided with terminal means protruding through said opening in said housing into electrical engagement with said opposite end of said fuses.
 32. In the combination defined by claim 31 wherein said circuit interrupters have casings disposed back-to-back in horizontal planes adjacent the bottom of said housing and said common plane, in which said fuse drawers is disposed, is horizontal and above said circuit interrupter casings and said circuit interRupters and said transformer are three phase and each said circuit interrupter has three poles and three insulating bushings extending horizontally from each end thereof carrying input and output terminals, and also including means for electrically commoning corresponding phase output terminals of said pair of circuit interrupters and electrically connecting them to one of said connector members.
 33. In the combination defined by claim 31 wherein said connector members are pivoted metallic bars and including fuse-clamping means on each said fuse drawer operable from the exterior of said housing, when said fuse drawers are inserted into said housing, for resiliently urging said connector member against said one end of said fuse to thereby push said opposite end against said terminal means on said transformer-insulating bushings, and means for latching said fuse drawers to said housing.
 34. In the combination defined by claim 7 wherein said fuse drawer latching means includes a latching member on each fuse drawer movable between a latching position wherein said fuse drawer is held against withdrawal from said housing and a released position wherein said drawer may be withdrawn and wherein said fuse-clamping means interferes with and holds said latching member in said latching position when said fuse is clamped against said terminal means on said insulating bushing and wherein said interlock means includes means to prevent operation of said fuse-clamping means in a direction to remove clamping pressure on said fuses when either of said circuit interrupters is in closed position.
 35. In the combination defined by claim 33 wherein said fuse drawer latching means includes a latching member on each fuse drawer movable between a latching position wherein said fuse drawer is held against withdrawal from said housing and a released position wherein said drawer may be withdrawn and wherein said fuse-clamping means interferes with and holds said latching member in said latching position when said fuse is clamped against said terminal means on said insulating bushing and wherein said interlock means includes means to prevent operation of said fuse-clamping means in a direction to remove clamping pressure on said fuses when either of said circuit interrupters is in closed position.
 36. In the combination defined by claim 34 and including means for providing universal motion of said terminal means on said transformer-insulating bushings relative to said bushings and for simultaneously maintaining continuous electrical connection between said fuses and said transformer, whereby said terminal means are in current transfer relation with said fuses even when said bushings and fuses are slightly misaligned.
 37. In the combination defined by claim 8 wherein said housing has a plurality of stationary insulating trays positioned in a horizontal plane above said circuit interrupters and supported on vertical standoff insulators and said fuse drawers are supported on and slidable along said trays and said trays and fuse drawers have registering apertures therein, when said fuse drawers are inserted into said housing, and said pivoted connector members protrude through said registering apertures into engagement with said one end of said fuses.
 38. In the combination defined by claim 12 and also including means for electrically commoning corresponding phase output terminals of said pair of circuit interrupters and electrically connecting them to one of said connector members and wherein said means for electrically commoning includes a plurality of bus bars having vertical portions electrically commoning corresponding phase output terminals of said first and second circuit interrupters and horizontal portions disposed above said circuit interrupters and said connector members are pivotally mounted and electrically connected to and supported on said horizontal portions of said bus bars.
 39. In the combination defined by claim 38 wherein each said fuse-clamping means includes rotatable threAded means on each said fuse drawer having a manual knob accessible from the exterior of said housing for engaging said pivoted connector member and actuating it in a direction longitudinally of said drawer to urge said other end of said fuse against said terminal means on said insulating bushing, and wherein said manual knob holds said latching member in said latching position when said fuse is clamped against said terminal means and said fuse-clamping means includes an elongated insulating rod on each fuse drawer having one end disposed adjacent said connector member when said drawer is inserted into said housing, means including a rotatable threaded member accessible from the exterior of said housing for actuating said rod longitudinally to push said connector member against said one end of said fuse, and spring means disposed between said insulating rod and said threaded member.
 40. In the combination defined by claim 17 wherein each said fuse means for latching said fuse drawer to said housing includes an eye on the front wall of said fuse drawer, a hook portion on said housing, and a latch member having an ear extending through said eye and engageable with said hook portion when said drawer is inserted into said housing, and wherein said threaded shaft is rotatable in a direction to urge said connector member against said fuse and to a position wherein said manual knob holds said latch member against motion and prevents removal of said ear from said hook portion, whereby said fuse drawer cannot be withdrawn from housing until both said circuit interrupters are open and said fuse-clamping means is released.
 41. In the combination defined by claim 31 wherein each said circuit interrupter is actuated between open and closed positions by a rotatable operating member and said interlock means includes a rotatable cam operatively connected to each said operating member, a cam follower engaging each said cam and contacting a limit position thereof when the corresponding circuit interrupter is closed, and means responsive to either cam follower engaging said limit position of the corresponding cam for interfering with removal of said fuse drawers from said housing including a plurality of mechanically ganged interfering arms each of which is rotatable to an interfering position wherein it blocks removal of one of said fuse drawers from said housing.
 42. In the combination defined by claim 41 wherein said connector members are pivoted metallic bars and including fuse-clamping means on each said fuse drawer operable from the exterior of said housing, when said fuse drawers are inserted into said housing, for resiliently urging said connector member against said one end of said fuse to thereby push said opposite end against said terminal means on said transformer-insulating bushing, means for latching said fuse drawers to said housing, and wherein said interlock means includes means to prevent operation of said fuse-clamping means in a direction to remove clamping pressure on said fuses when either of said circuit interrupters is in closed position.
 43. In the combination defined by claim 42 wherein said means for interfering with removal of said fuse drawers includes a plurality of mechanically ganged interfering arms each of which is rotatable to an interfering position wherein it blocks withdrawal of one of said fuse drawers from said housing and said cam followers are generally parallel rods adapted to be translated longitudinally by said cams and said means for preventing simultaneous operation of both of said circuit interrupters to closed position includes an elongated rocker bar disposed transverse to and operatively connected adjacent its ends to said cam follower rods and a stationary stop disposed adjacent said rocker bar intermediate its ends and positioned to permit pivotal movement of said rocker bar about said stop, when one cam follower rod is moved longitudinally, but to interfere with transverse translation of said rocker bar when both said cams are rOtated in a direction to actuate said cam follower rods longitudinally.
 44. In the combination defined by claim 25 wherein said cam followers are generally parallel rods adapted to be translated longitudinally by said cams and said means for preventing simultaneous operation of both of said circuit interrupters to closed position includes an elongated rocker bar disposed transverse to and operatively connected adjacent its ends to said cam follower rods and a stationary stop disposed adjacent said rocker bar intermediate its ends and positioned to permit pivotal movement of said rocker bar about said stop, when one cam follower rod is moved longitudinally, but to interfere with transverse translation of said rocker bar when both cams are rotated in a direction to actuate said cam follower rods longitudinally.
 45. In the combination defined by claim 33 wherein each of said circuit interrupters is actuated between open and closed positions by a rotatable operating member and said means for preventing simultaneous operation of both circuit interrupters to closed position has associated with each said circuit interrupter a rotary cam operatively connected to said rotatable operating member, a cam follower rod associated with said cam and engaging a limit position thereon when said circuit interrupter is in closed position, and means including an elongated rocking bar operatively connected to said cam follower rods at its opposite ends and a stationary stop member adjacent the middle and interfering with transverse translation of said elongated bar for preventing simultaneous rotation of both said eccentric cams to the position wherein said limit position thereon engages said cam follower rod.
 46. In the combination defined by claim 11 and including latching means on each said fuse drawer movable between a latching position wherein said fuse drawer is held against withdrawal from said housing and a released position wherein said drawer may be withdrawn and wherein said means for urging said connector member against one end of said fuse interferes with and holds said latching means in said latching position.
 47. In the combination defined by claim 46 wherein said interlock means includes means to prevent release of said means for urging said connector member against one end of said fuse when either said first or said second circuit interrupter is in closed position.
 48. In the combination defined by claim 47 wherein said housing has a plurality of stationary trays positioned in a horizontal plane and said fuse drawers are supported on and slidable on said trays, and wherein said trays and fuse drawers have registering apertures therein, when said fuse drawers are inserted into said housing, and said connector members protrude through said registering apertures into engagement with said one end of said fuses.
 49. In combination, a housing, a high-voltage circuit interrupter within said housing operable between open and closed positions and having an output terminal and also having an input terminal adapted to be connected to a high-voltage electrical cable, a fuse drawer reciprocable into and out of said housing, an elongated fuse on each said fuse drawer, a movable connector member engaging one end of said fuse on said fuse drawer, when said fuse drawer is inserted into said housing, and being electrically connected to said output terminal, means for latching said fuse drawer to said housing, and fuse-clamping means on said fuse drawer operable from the exterior of said housing, when said fuse drawer is inserted into said housing, for urging said connector member against one end of said fuse, said fuse-clamping means interfering with and preventing release of said drawer-latching means when said connector member is urged against said one end of said fuse.
 50. In the combination defined by claim 49 and including interlock means for preventing operation of said fuse-clamping means in a direction to permit said connector member to disengage said one end of said fuse when said circuit interrupter is in closed position.
 51. In the combination defined by claim 50 wherein said housing has a stationary tray and said fuse drawer is supported on and slidable on said tray and wherein said tray and fuse drawer have registering apertures, when said fuse drawer is inserted into said housing, and said connector member is pivoted and protrudes through said registering apertures into engagement with said one end of said fuse.
 52. In the combination defined by claim 50 wherein said connector member is pivoted and said means for latching said fuse drawer includes a latching member on said fuse drawer movable between a latching position wherein said fuse drawer is held against withdrawal from said housing and a released position wherein said drawer may be withdrawn and said fuse-clamping means includes rotatable threaded means on said fuse drawer having a manual knob accessible from the exterior of said housing for engaging said pivoted connector member and actuating it in a direction longitudinally of said drawer and against said one end of said fuse, and wherein said manual knob holds said latching member in said latching position when said connector member is urged against said one end of said fuse.
 53. In the combination defined by claim 52 and including interlock means for preventing withdrawal of said fuse drawer from said housing when said circuit interrupter is closed.
 54. In the combination defined by claim 53 wherein said interlock means includes an interfering arm mounted on said housing for rotation between an interfering position wherein it blocks rotation of said manual knob and withdrawal of said fuse drawer from said housing when said circuit interrupter is closed and a noninterfering position wherein said manual knob and said threaded means can be rotated until said pivoted connector member disengages said one end of said fuse and said latching member can be moved to said released position.
 55. In the combination defined by claim 54 wherein said fuse drawer has an aperture therein and said fuse-clamping means includes an elongated insulating rod on said fuse drawer movable longitudinally thereof, an insulating shoe disposed adjacent one end of said insulating rod and depending through said aperture in said drawer and being adapted to engage said connector member and pivot it upwards against said one end of said fuse when said drawer is inserted into said housing, and spring means disposed between and operatively connecting said rotatable threaded means and said insulating rod. 